Novel rotary chemical mechanical polishing on an integral impeller. (June 2021) - Liao, Longxing
Graphical abstract: Highlights: High quality and efficiency chemical mechanical polishing (CMP) for an integral propeller is performed by a developed polisher and novel CMP slurry. A novel CMP slurry consists of phosphoric acid (H3 PO4 ), hydrogen peroxide (H2 O2 ), nicotinic acid (NA) and silicon carbide (SiC). The polishing time of the developed CMP is 2 h for an integral propeller, which is faster than the conventional manual polishing on an integral propeller by twenty times. After CMP, the processing defects such as pits, tool marks and vibration marks on the blade surface and hub became faint. Furthermore, the low damage layer thickness shows significant improvement for the proposed method. Abstract: Traditional polishing on an integral impeller is labour intensive owing to its complicated curved surfaces. In this study, a novel rotary chemical mechanical polishing (R-CMP) for an integral impeller has been proposed using a developed polisher and a novel CMP slurry to improve efficiency and quality as compared to the traditional polishing method. The novel slurry consists of phosphoric acid (H3 PO4 ), hydrogen peroxide (H2 O2 ), nicotinic acid (NA) and silicon carbide (SiC). A model for predicting the surface roughness is established, according to the R-CMP process parameters during polishing an integral impeller, which is in good agreement with experimental results. It was found out that the polishing mechanism of R-CMP consists of four processing steps: oxidation, dissolution, chelating and removal. After R-CMP on an integral impeller, the surface roughness Ra of the blade root is reduced from 1.664 to 0.559 μm, and the thickness of the damage layer is decreased from 900 to 350 nm. The polishing time is 2 h, which is faster than the conventional manual polishing on an integral propeller by twenty times. The findings in this research open a new pathway to polish an integral high performance component with complicated curved surfaces using immersive CMP at high efficiency and high quality, without the need to exert external pressure.